Fine specificity of T cells reactive to human PDC-E2 163-176 peptide, the immunodominant autoantigen in primary biliary cirrhosis: Implications for molecular mimicry and cross-recognition among mitochondrial autoantigens

Hirohisa Shigematsu, Shinji Shimoda, Minoru Nakamura, Sho Matsushita, Yasuharu Nishimura, Norihiro Sakamoto, Yasunori Ichiki, Yoshiyuki Niho, M. Eric Gershwin, Hiromi Ishibashi

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60 Scopus citations

Abstract

The anti-mitochondrial antibody response in primary biliary cirrhosis (PBC) is primarily directed at E2 components of PDC, OGDC, and BCOADC, and E3BP. Previous work has shown that the immunodominant autoreactive T- cell epitope is the PDC-E2 163-176 peptide, restricted by HLA DR53. To address molecular mimicry and cross-recognition among mitochondrial autoantigens, we analyzed reactivity, including agonism and antagonism assays, to a series of single amino acid-substituted peptides using cloned T-cell lines in PBC and controls. Interestingly, fine specificities were unique for every single T-cell clone, but the clones could be categorized into two distinct groups based on recognition motifs of the T-cell receptor (TCR) ligand: Group A 170ExDK173 and group B 168ElExD172. 170E is the most critical TCR contact residue for both groups of cloned T-cell lines, whereas 173K and 168E are the critical TCR contact residues for group A and group B cloned T-cell lines, respectively. More importantly, some group A-cloned T-cell lines cross-reacted to human E3BP 34-47, human OGDC-E2 100-113, and several peptides derived from various microbial proteins carrying an ExDK motif, whereas group B-cloned T-cell lines reacted only to E3BP 34-47 carrying an ElExD motif. Furthermore, an RGxG motif was exclusively found in the complementarity-determining region (CDR3) of the TCR Vβ in the group B-cloned T-cell lines, while G, S, and/or R were frequently found in the CDR3 of the TCR Vβ in the group A-cloned T-cell lines. These data provide a framework for understanding molecular mimicry among mitochondrial antigens.

Original languageEnglish (US)
Pages (from-to)901-909
Number of pages9
JournalHepatology
Volume32
Issue number5
StatePublished - 2000

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ASJC Scopus subject areas

  • Hepatology

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